The present invention relates to a differential impulse conveyor assembly and to a method for moving goods along a conveyor tray. More particularly, this invention relates to such an assembly and a method in which a reversible motor is utilized for powering the conveyor tray in a slow forward and fast backward movement.
U.S. Pat. No. 5,794,757 discloses a differential impulse conveyor having a generally elongate horizontal or slightly inclined tray or pan for the transport of goods along the tray. The tray is moved slowly forward and is then pulled rearwardly at a high return speed so that the goods slide along the tray, thereby effectively transporting the goods along the conveyor tray. Such differential impulse conveyors are utilized for many applications (such as food handling) when conveyor cleanliness, low noise, and/or minimal product damage are desired.
The ""757 patent discloses an electronic controller for controlling the rotational speed of the motor shaft to cause the motor shaft to rotate at a first speed for forward movement of the tray and to rotate at a substantially faster second speed for a faster backward movement of the tray, thereby moving goods along the tray in a forward direction. The motor shaft rotates in a single direction of rotation and the tray is connected to cranks driven by the motor shaft to effect a desired forward and backward movement of the tray. Further, counterweights connected to cranks for such movement are provided out of phase with the conveyor tray movement to reduce undesirable conveyor vibration and/or mechanical knock in the drive system. An electronic controller may repeatedly vary the rotational speed of the motor shaft and is programmable for easily varying the overall speed of the motor and the instantaneous rotational speed of the drive shaft as desired to optimize the movement of the goods along the conveyor tray. The cranks and crank assemblies required as a result of the rotation of the motor shaft in a single rotational direction may be costly and may require substantial maintenance.
One object of the present invention is to provide a conveyor drive mechanism for the tray at a slow-forward and fast-backward movement which substantially reduces or totally eliminates the utilization of cranks, crank assemblies and eccentric movements.
The present invention is directed to a differential impulse conveyor having a conveyor drive mechanism for a tray for moving goods along the tray in a desired forward and backward movement of the tray. The conveyor drive mechanism utilizes a reversible motor for rotating the motor shaft in opposed directions of rotation. An electronic controller for the motor effects rotation of the motor shaft in one direction at one speed and rotation of the motor shaft in an opposite direction at a different speed, thereby providing a slow forward linear movement of the tray during one time or half cycle, and a fast return or rearward movement of the tray during a second time or half cycle.
The drive mechanism between the motor shaft and the tray to provide the forward and backward linear movement of the tray is illustrated by several embodiments. A first embodiment of the invention utilizes a rack and pinion assembly in which the pinion is mounted between an upper rack and a lower rack with the upper rack secured to the tray. A sprocket and sprocket chain between the motor and pinion results in a forward and backward movement of the upper rack and tray upon reversal of the rotational direction of the motor shaft. Linkage assemblies support the racks for the desired tray movement. A counterweight may be connected to the lower rack to minimize vibration and knocking.
A second embodiment of the drive mechanism between the motor shaft and the tray provides the desired forward and backward movement of the tray by utilizing a pair of timing belts mounted on support arms or links of upper and lower linkage assemblies. The upper support arm on the upper linkage assembly has one timing belt mounted thereon and is secured to the tray for movement of the tray back and forth. Each timing belt is trained over idler rollers on opposed sides of the sprocket for engaging a respective belt. A counterweight is mounted on the lower linkage assembly which moves in an opposite direction from the tray and upper linkage assembly, thereby minimizing vibration and knock problems. Only a single counterweight is required when embodiments are suggested in view of the two discussed above.
An electronic controller is programmed from a preselected acceleration/deceleration curve. The curve may be provided from a graph which is plotted to set forth the tray travel in inches and the tray velocity in inches per second as a function of the angular position of the motor shaft. The relevant factors include tray travel, tray velocity, tray acceleration, tray deacceleration, and torque exerted by the motor shaft. The controller may be programmed to produce the desired output to the motor for rotating the motor shaft at a first speed in one direction during each first half cycle rotation, and then rotating in the motor shaft in the reverse direction at a second speed greater than the first speed during each second half cycle of rotation. As a result of the reversing the direction of rotation of the motor shaft, a simplified conveyor drive mechanism has been provided for interconnecting the motor shaft with the tray or pan for the desired forward and backward movement. Crank and crank arms assemblies utilized heretofore for the drive mechanism may be eliminated by the present invention.
These and further objects, features, and advantages of the present invention will become apparent from the following detailed description wherein reference is made to the Figures in the accompanying drawings.